High-tension transformer



' W. HESS.

HIGH TENS I ON TRANSFORMER Filed Aug 15, 1927 2 Sheets-Sheet 1 Fig. I.

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UNITED STATES PATENT OFFICE.

WILHELM HESS, OF BASEL, SWITZERLAND, ASSIGNOR TO THE FIR-M EMIL HAEFELY85 CIE. A. G., OF BASEL, SWITZERLAND.

HIGH-TENSION TRANSFORMER.

Application filed August 15, 1927, Serial No. 213,141, and in GermanyAugust 21, 1926.

This invention relates to air-insulated transformers for high tensionsand has for its object to provide an improved transformer of thischaracter.

It is known to employ, for the purpose of insulating transformers of theoil-insulated type, insulating devices comprising condenser elementsbetween the high and low voltage windings, these devices having fortheir object to ensure a uniform potential distribution and thus toarrive at a minimum expense of material.

In transformers of the oil-insulated type it has, however, been shown inpractice, that no great purpose is served by employing such insulatingcondenser devices, as the insulating properties of the oil arethemselves so great that no appreciable reduction in the thickness ofthe insulation required is attained.

On the other hand, however, in an air transformer of the kind in whichan insulating air jacket is provided between the high and low voltagewindings, as in the U. S. specification No. 1,523,891, on account of thecomparatively large air jacket necessary for efficient insulation, aconsiderable increase in the stray voltage of the transformer occurs,especially when the air transformer has its windings connected incascade, like an autotransformer, and uses, a so called compensatingwinding.

According to the invention, therefore, an air-insulated transformer ofthe kind just described is provided with an insulating element,preferably constituted by a condenser device, arranged between theexciting and the compensating windings of the transformer, this beingthe position at which, in consequence of the comparatively short axiallength of the exciting winding, the main portion of the stray voltageoccurs, so that a considerable improvement in the voltage drop andeificiency of the transformer as a whole is attained, while at the sametime, permitting the dimensions of the transformer to be reduced.

The invention will now be described by way of example, with reference tothe accompanying drawing in which:

Figures 1, 2 and 3 are diagrammatic views illustrating three differentembodiments of the invention.

Figure 4 shows a diagram of the windings of the first arrangement forexample.

Figures 1 and 1 represent an air-insulated transformer of the kinddisclosed by the U. S. specification No. 1,523,891 and arranged as anautotransformer, a being the exciting or primary winding and g, h thesecondary or high tension windings connected therewith, as is well knownin autovtransformer connection systems. 0 is the iron core. On the samecore 0 and as near as possible thereto is mounted an auxiliary winding binductively coupled with the exciting winding a. This auxiliary winding6 is connected with the auxiliary windings e, f on' the legs of thecore, which are themselves inductively coupled with the correspondinghigh tension windings g, h, the iron core 0, as is usual, being arrangedto be insulated against earth. These auxiliary windings constitute whatis termed here compensating winding inasmuch as they have to produce acompensating effect on the potential stresses, said compensating windingbeing at the same potential as the core 0. The arrangement of suchcompensating windings is disclosed for example in the U. S. Re.specification No. 15,951. A sufficiently large insulating air jacket onis provided between the high and low tension windings e, f and g, h, asdescribed in the U. S. specification No. 1,523,891.

An insulating element (Z of suitable material and dimensions is arrangedbetween the windings a and b, in order to permit of the exciting winding(B being approached nearer than hitherto to the winding 5, thisobviating or reducing losses due to leakage.

In the embodiment of the invention illustrated in Figure 2, theinsulating element (Z is arranged to extend between the windings e and 9throughout the axial length of these windings, so as to serve asadditional insulating means for the high tension winding 9', but it mayalso be arranged so as to extend for a part only of the axial length ofthe windings e and g, the function of the air jacket not being affectedthereby. Furthermore the high tension winding 9 is arranged to extendover the exciting winding a.

Referring now to Figure 3, it will be evident that the embodimentillustrated in this figure is similar to that illustrated in Figure 1.The insulating element, however, is constituted by a condenser devicethat is to say by a cylinder 01 composed of alternate layers or strataof insulating and conducting material. The outer conducting layer of thecondenser device (Z is preferably electrically connected to the excitingwinding a, the inner layer being electrically connected to thecompensating winding 6.

In this embodiment of the invention it may be advisable to build up thecondenser device of several similar condenser elements arrangedcoaxially within one another and leaving a suitable air space betweenthem, this arrangement permitting the heat gen erated to escape morereadily thanin the case of a condenser without air spaces.

It will be evident that the invention is not limited to the particularconstruction and arrangement of parts herein above described which maybe varied as desired to suit particular requirements within the scope ofthe invention.

' What I claim is:

1. An air-insulated high tension transformer, having an earth insulatediron core, an exciting or primary winding, a secondary and secondarywindings and several coaxially arranged insulating elements, additionalto air insulation, arranged between said exciting and compensatingwindings and having an air space between them, substantially as and forthe purpose described.

In witness whereof I have hereunto signed my name this 29thday of July,1927.

VVILHELM HESS.

